Nature has an ironic sense of humor: For a lot of women, the idea of having a baby is downright terrifying until one day, it suddenly isn’t. But in many cases that day doesn’t come until right around the time the baby-making window of opportunity is starting to close, and fast.

While our fertility rates gradually decline as we get older, there’s a drop in our ability to reproduce between ages 32 and 37, with a more rapid fall after that, according to the American College of Obstetricians and Gynecologists (ACOG). That biological deadline is one of the reasons actress Olivia Munn, 35—of Iron Man 2 and Mortdecai fame—decided to freeze her eggs. Last week on the podcastAnna Faris Is Unqualified, Munn talked about how much relief it has brought her: “I think that every girl should do it,” she said. “It’s also just like, why not do it.”

In reality, the decision is a lot more complicated than that. Before you call your local fertility clinic, there are a few things you should know about the procedure technically known as oocyte cryopreservation.

It’s not a one-step process

The egg freezing procedure takes a few weeks, says Mindy Christianson, MD, an assistant professor of gynecology and obstetrics at Johns Hopkins University and a physician at the Johns Hopkins Fertility Center. First steps can include a baseline ultrasound and a blood test. After that, you’ll start giving yourself injections of fertility hormones at home for about a week or so. The hormones will hopefully spur your ovaries to produce, say, 20 eggs, instead of just one. (Luckily, the needles aren’t painful, says Dr. Christianson. They’re similar to insulin pens.) Throughout the process, you’ll need to return to your doctor’s office for follow-up blood tests and ultrasounds.

Egg retrieval is no day at the spa

Your doctors will probably gather your eggs (sorry) with ultrasound guidance. They’ll stick a long, thin needle into your vagina, then grab the eggs and prep them for freezing. You’ll be under sedation for that, naturally. The good news: You’ll probably only have mild cramping afterwards, and with a pain pill, you should be okay. (Though wait a few days to exercise, since your ovaries will be enlarged.)

It’s pretty expensive

After tallying up the costs of the injections, doctor’s visits, and the procedure itself, you’re probably looking at a bill that can total $10,000 to $15,000, says Dr. Christianson. And then there’s the cost of storing the eggs, which may set you back anywhere from $500 to $800 a year.

However, the price tag looks better after you turn 40. A 2012 study in the journal Fertility and Sterility found that a woman trying to get pregnant at age 40 would save $15,000 if she froze her eggs at age 35. That’s because the costs of using assisted reproductive technology to get pregnant after you’re 40 can be more expensive than freezing your eggs at a younger age.

If you are interested in exploring the possibility of freezing your eggs, you may want to start by looking up the clinics near you. The Centers for Disease Control and Prevention keeps this database of fertility clinics in every state with statistics on their success rates.